Magnetic information on hard drives is accessed by a read head that must move ra

Question

Magnetic information on hard drives is accessed by a read head that must move rapidly back and forth across the disk. The force to move the head is generally created with a voice coil actuator, a flat coil of fine wire that moves between the poles of a strong magnet, as in the figure. Assume that the coil is a square 1.0 cm on a side made of 210 turns of fine wire with total resistance 1.4 ohm. The field between the poles of the magnet is 0.25 T assume that the field does not extend beyond the edge of the magnet. The coil and the mount that it rides on have a total mass of 13 g. (Figure 1) Express your answer to two significant figures and include the appropriate units. I 3.6 If the current is clockwise viewed from above, what is the direction of the net force on the coil? Directed up in the "Top view" figure. Directed down in the "Top view figure Directed to the left in the "Top view" figure. Directed to the right in the "Top view" figure What is the magnitude of the net force on the coil?

Explanation / Answer

B) Directed to the right in the top view figure.
It is determined by right hand rule.
Right hand rule: Take your right hand in the direction of L(in the direction of current) and rurl your fingers in the direction of magnetic field then your thumb indicates the direction of magnetic force.

C)

F = B*I*L*sin(90)

= 0.25*3.6*0.01

= 9*10^-3 N

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